Commonly-owned U.S. patent application Ser. No. 08/152,812 filed 16 Nov. 1993 (now U.S. Pat. No. 4,576,211, issued 19 Dec. 1995), and its counterpart commonly-owned “divisional” U.S. patent application Ser. No. 08/457,479 filed 1 Jun. 1995 (status: pending) and Ser. No. 08/570,230 filed 11 Dec. 1995 (status: pending), all by KHANDROS, disclose methods for making resilient interconnection elements for microelectronics applications involving mounting an end of a flexible elongate core element (e.g., wire “stem” or “skeleton”) to a terminal on an electronic component, and coating the flexible core element and adjacent surface of the terminal with a “shell” of one or more materials having a predetermined combination of thickness, yield strength and elastic modulus to ensure predetermined force-to-deflection characteristics of the resulting spring contacts. Exemplary materials for the core element include gold. Exemplary materials for the coating include nickel and its alloys. The resulting spring contact element is suitably used to effect pressure, or demountable, connections between two or more electronic components, including semiconductor devices.
Commonly owned U.S. patent application Ser. No. 08/340,144 filed 15 Nov. 1994 and its corresponding PCT Patent Application No. PCT/US94/13373 filed 16 Nov. 1994 (published as WO95/14314, 26 May 1995), disclose a number of applications for the aforementioned spring contact element, and also disclose techniques for fabricating contact pads at the ends of the spring contact elements. For example, in FIG. 14 thereof, a plurality of negative projections or holes, which may be in the form of inverted pyramids ending in apexes, are formed in the surface of a sacrificial layer (substrate). These holes are then filled with a contact structure comprising layers of material such as gold or rhodium and nickel. A flexible elongate element is mounted to the resulting contact structure and can be overcoated in the manner described hereinabove. In a final step, the sacrificial substrate is removed. The resulting spring contact has a contact pad having controlled geometry (e.g., sharp points) at its free end.
Commonly-owned U.S. patent application Ser. No. 08/452,255 filed 26 May 95 (status: pending) and its corresponding PCT Patent Application No. PCT/US95/14909 filed 13 Nov. 1995 (published as WO96/17278, 6 Jun. 1996), disclose additional techniques and metallurgies for fabricating contact tip structures on sacrificial substrates, as well as techniques for transferring a plurality of spring contact elements mounted thereto, en masse, to terminals of an electronic component (see, e.g., FIGS. 11A-11F and 12A-12C therein).
Commonly-owned U.S. patent application Ser. No. 08/788/740 filed 24 Jan. 1997 (status: pending) and its corresponding PCT Patent Application No. PCT/US96/08107 filed 24 May 1996 (published as WO96/37332, 28 Nov. 1996), discloses techniques whereby a plurality of contact tip structures (see, e.g., #620 in FIG. 6B therein) are joined to a corresponding plurality of elongate contact elements (see, e.g., #632 of FIG. 6D therein) which are already mounted to an electronic component (#630). This patent application also discloses, for example in FIGS. 7A-7E therein, techniques for fabricating “elongate” contact tip structures in the form of cantilevers. The cantilever tip structures can be tapered, between one end thereof and an opposite end thereof. The cantilever tip structures of this patent application are suitable for mounting to already-existing (i.e., previously fabricated) raised interconnection elements (see, e.g., #730 in FIG. 7F) extending (e.g., free-standing) from corresponding terminals of an electronic component (see. e.g., #734 in FIG. 7F).
Commonly owned U.S. patent application Ser. No. 08/819,464 filed 17 Mar. 1997 (status: pending) and its corresponding PCT Patent Application number US97/08606 filed 15 May 1997 (published as WO97/43653, 20 Nov. 1997), incorporated by reference herein, disclose a number of processes and metallurgies for prefabricating contact tip structures on sacrificial substrates, for later joining to ends of spring contact elements, as well as mechanisms for releasing prefabricated components of spring contact elements from the sacrificial substrates. Many of the processes, metallurgies and mechanisms disclosed therein are directly applicable to the methods and apparatus of the present invention.
Commonly-owned, copending U.S. patent application Ser. No. 08/802,054 filed 18 Feb. 1997, and its corresponding PCT Patent Application No. US97/08271 disclose a technique for making microelectronic contact structures by masking and etching grooves into a sacrificial substrate (e.g., a silicon wafer), then depositing one or more layers of metallic material into the grooves, then transferring the resulting structures onto an electronic component such as by brazing, then removing the sacrificial substrate so that the fabricated structures are secured at one end to the electronic component and have another end for contacting another electronic component and function as spring contact elements. The present invention takes the concept a step further, providing an alternate technique for fabricating such spring contact elements and mounting them to terminals of electronic components.
Commonly-owned, copending U.S. patent application Ser. No. 08/852,152 filed 6 May 1997, and its corresponding PCT Patent Application number US97/08634 filed 15 May 1997 disclose a technique for making microelectronic contact structures by applying a series of masking layers patterned with openings onto a substrate such as a semiconductor device, then depositing one or more layers of metallic material into the openings, then removing the masking layers. This results in a plurality of spring contact elements having been fabricated on the substrate at lithographically-defined locations.
The present invention addresses and is particularly well-suited to making interconnections to modern microelectronic devices having their terminals (bond pads) disposed at a fine-pitch. The invention is useful for devices with arbitrarily large pitch, but also is particularly useful for fine pitch. As used herein, the term “fine-pitch” refers to microelectronic devices that have their terminals disposed at a spacing of less than 5 mils, such as 2.5 mils or 65 μm. As will be evident from the description that follows, this is preferably achieved by taking advantage of the close tolerances that readily can be realized by using lithographic rather than mechanical techniques to fabricate the contact elements.
An exemplary application for making fine-pitch pressure connections between electronic components can be found in commonly-owned U.S. patent application Ser. No. 08/554,902 filed 09 Nov. 1995 by ELDRIDGE, GRUBE, KHANDROS and MATHIEU (status: pending) and its corresponding PCT Patent Application No. PCT/US95/14844 filed 13 Nov. 1995 (published as WO96/15458, 23 May 1996) which disclose a probe card assembly including elongate resilient (spring) contact elements mounted to a “space transformer” component. As used herein, a space transformer is a multilayer interconnection substrate having terminals disposed at a first pitch on a one surface thereof and having corresponding terminals disposed at a second pitch on an opposite surface thereof, and is used to effect “pitch-spreading” from the first pitch to the second pitch. In use, the free ends (tips) of the elongate spring contact elements make pressure connections with corresponding terminals on an electronic component being probed (e.g., tested).
Another example of an application for fine pitch spring contact elements can be found in commonly-owned U.S. patent application Ser. No. 08/784,862 filed 15 Jan. 1997 by KHANDROS and PEDERSEN (status: pending) and its corresponding PCT Patent Application No. US97/08604 filed 15 May 1997 (published as WO97/43656, 20 Nov. 1997) which disclose mounting springs on active semiconductor devices.